Vapor compression system and method for controlling conditions in ambient surroundings

ABSTRACT

A vapor compression system including an evaporator, a compressor, and a condenser interconnected in a closed-loop system and a method of operating such a system. The method includes the conversion of expanded liquid heat transfer fluid from a liquid form to a high quality liquid vapor mixture before delivery to the evaporator. In one embodiment, the heat transfer surface of the evaporator coil is smaller than that required to obtain an equivalent evaporator capacity when the expanded liquid heat transfer fluid is not converted from a liquid form to a high quality liquid vapor mixture

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.10/948,446, filed Sep. 23, 2004, which is a continuation-in-part of U.S.patent application Ser. No. 10/129,339, filed May 2, 2002, which is aNational Stage of PCT/US00/14648, filed May 26, 2000. PCT/US00/14648 isa continuation-in-part of P.C.T. application PCT/US00/00663, filed Jan.11, 2000, which was published in English and designated the UnitedStates and a continuation-in-part of U.S. patent application Ser. No.09/431,830, filed Nov. 2, 1999, now U.S. Pat. No. 6,185,958. Thecontents of these prior applications are incorporated by reference.

BACKGROUND

In a closed-loop vapor compression cycle, the heat transfer fluidchanges state from a vapor to a liquid in the condenser, giving offheat, and changes state from a liquid to a vapor in the evaporator,absorbing heat during vaporization. A typical vapor-compression systemincludes a compressor for pumping a heat transfer fluid, such as afreon, to a condenser, where heat is given off as the vapor condensesinto a liquid. The liquid flows through a liquid line to a thermostaticexpansion valve, where the heat transfer fluid undergoes a volumetricexpansion. The heat transfer fluid exiting the thermostatic expansionvalve is a low quality liquid vapor mixture. As used herein, the term“low quality liquid vapor mixture” refers to a low pressure heattransfer fluid in a liquid state with a small presence of flash gas thatcools off the remaining heat transfer fluid, as the heat transfer fluidcontinues on in a sub-cooled state. The expanded heat transfer fluidthen flows into an evaporator, where the liquid refrigerant is vaporizedat a low pressure absorbing heat while it undergoes a change of statefrom a liquid to a vapor. The heat transfer fluid, now in the vaporstate, flows through a suction line back to the compressor. Sometimes,the heat transfer fluid exits the evaporator not in a vapor state, butrather in a superheated vapor state.

In one aspect, the efficiency of the vapor-compression cycle dependsupon the ability of the vapor compression system to maintain the heattransfer fluid as a high pressure liquid upon exiting the condenser. Thecooled, high-pressure liquid must remain in the liquid state over thelong refrigerant lines extending between the condenser and thethermostatic expansion valve. The proper operation of the thermostaticexpansion valve depends upon a certain volume of liquid heat transferfluid passing through the valve. As the high-pressure liquid passesthrough an orifice in the thermostatic expansion valve, the fluidundergoes a pressure drop as the fluid expands through the valve. At thelower pressure, the fluid cools an additional amount as a small amountof flash gas forms and cools of the bulk of the heat transfer fluid thatis in liquid form. As used herein, the term “flash gas” is used todescribe the pressure drop in an expansion device, such as athermostatic expansion valve, when some of the liquid passing throughthe valve is changed quickly to a gas and cools the remaining heattransfer fluid that is in liquid form to the corresponding temperature.

This low quality liquid vapor mixture passes into the initial portion ofcooling coils within the evaporator. As the fluid progresses through thecoils, it initially absorbs a small amount of heat while it warms andapproaches the point where it becomes a high quality liquid vapormixture. As used herein, the term “high quality liquid vapor mixture”refers to a heat transfer fluid that resides in both a liquid state anda vapor state with matched enthalpy, indicating the pressure andtemperature of the heat transfer fluid are in correlation with eachother. A high quality liquid vapor mixture is able to absorb heat veryefficiently since it is in a change of state condition. The heattransfer fluid then absorbs heat from the ambient surroundings andbegins to boil. The boiling process within the evaporator coils producesa saturated vapor within the coils that continues to absorb heat fromthe ambient surroundings. Once the fluid is completely boiled-off, itexits through the final stages of the cooling coil as a cold vapor. Oncethe fluid is completely converted to a cold vapor, it absorbs verylittle heat. During the final stages of the cooling coil, the heattransfer fluid enters a superheated vapor state and becomes asuperheated vapor. As defined herein, the heat transfer fluid becomes a“superheated vapor” when minimal heat is added to the heat transferfluid while in the vapor state, thus raising the temperature of the heattransfer fluid above the point at which it entered the vapor state whilestill maintaining a similar pressure. The superheated vapor is thenreturned through a suction line to the compressor, where thevapor-compression cycle continues.

For high-efficiency operation, the heat transfer fluid should changestate from a liquid to a vapor in a large portion of the cooling coilswithin the evaporator. As the heat transfer fluid changes state from aliquid to a vapor, it absorbs a great deal of energy as the moleculeschange from a liquid to a gas absorbing a latent heat of vaporization.In contrast, relatively little heat is absorbed while the fluid is inthe liquid state or while the fluid is in the vapor state. Thus, optimumcooling efficiency depends on precise control of the heat transfer fluidby the thermostatic expansion valve to insure that the fluid undergoes achange of state in as large of cooling coil length as possible. When theheat transfer fluid enters the evaporator in a cooled liquid state andexits the evaporator in a vapor state or a superheated vapor state, thecooling efficiency of the evaporator is lowered since a substantialportion of the evaporator contains fluid that is in a state whichabsorbs very little heat. For optimal cooling efficiency, a substantialportion, or an entire portion, of the evaporator should contain fluidthat is in both a liquid state and a vapor state. To insure optimalcooling efficiency, the heat transfer fluid entering and exiting fromthe evaporator should be a high quality liquid vapor mixture.

The thermostatic expansion valve plays an important role and regulatingthe flow of heat transfer fluid through the closed-loop system. Beforeany cooling effect can be produced in the evaporator, the heat transferfluid has to be cooled from the high-temperature liquid exiting thecondenser to a range suitable of an evaporating temperature by a drop inpressure. The flow of low pressure liquid to the evaporator is meteredby the thermostatic expansion valve in an attempt to maintain maximumcooling efficiency in the evaporator. Typically, once operation hasstabilized, a mechanical thermostatic expansion valve regulates the flowof heat transfer fluid by monitoring the temperature of the heattransfer fluid in the suction line near the outlet of the evaporator.The heat transfer fluid upon exiting the thermostatic expansion valve isin the form of a low pressure liquid having a small amount of flash gas.The presence of flash gas provides a cooling affect upon the balance ofthe heat transfer fluid in its liquid state, thus creating a low qualityliquid vapor mixture. A temperature sensor is attached to the suctionline to measure the amount of superheating experienced by the heattransfer fluid as it exits from the evaporator. Superheat is the amountof heat added to the vapor, after the heat transfer fluid has completelyboiled-off and liquid no longer remains in the suction line. Since verylittle heat is absorbed by the superheated vapor, the thermostaticexpansion valve meters the flow of heat transfer fluid to minimize theamount of superheated vapor formed in the evaporator. Accordingly, thethermostatic expansion valve determines the amount of low-pressureliquid flowing into the evaporator by monitoring the degree ofsuperheating of the vapor exiting from the evaporator.

In addition to the need to regulate the flow of heat transfer fluidthrough the closed-loop system, the optimum operating efficiency of thevapor compression system depends upon periodic defrost of theevaporator. Periodic defrosting of the evaporator is needed to removeicing that develops on the evaporator coils during operation. As ice orfrost develops over the evaporator, it impedes the passage of air overthe evaporator coils reducing the heat transfer efficiency. In acommercial system, such as a refrigerated display cabinet, the build upof frost can reduce the rate of air flow to such an extent that an aircurtain cannot form in the display cabinet. In commercial systems, suchas food chillers, and the like, it is often necessary to defrost theevaporator every few hours. Various defrosting methods exist, such asoff-cycle methods, where the refrigeration cycle is stopped and theevaporator is defrosted by air at ambient temperatures. Additionally,electrical defrost off-cycle methods are used, where electrical heatingelements are provided around the evaporator and electrical current ispassed through the heating coils to melt the frost.

In addition to off-cycle defrost systems, vapor compression systems havebeen developed that rely on the relatively high temperature of the heattransfer fluid exiting the compressor to defrost the evaporator. Inthese techniques, the high-temperature vapor is routed directly from thecompressor to the evaporator. In one technique, the flow of hightemperature vapor is dumped into the suction line and the vaporcompression system is essentially operated in reverse. In othertechniques, the high-temperature vapor is pumped into a dedicated linethat leads directly from the compressor to the evaporator for the solepurpose of conveying high-temperature vapor to periodically defrost theevaporator. Additionally, other complex methods have been developed thatrely on numerous devices within the vapor compression system, such asbypass valves, bypass lines, heat exchangers, and the like.

In an attempt to obtain better operating efficiency from conventionalvapor-compression systems, the refrigeration industry is developingsystems of growing complexity. Sophisticated computer-controlledthermostatic expansion valves have been developed in an attempt toobtain better control of the heat transfer fluid through the evaporator.Additionally, complex valves and piping systems have been developed tomore rapidly defrost the evaporator in order to maintain high heattransfer rates. While these systems have achieved varying levels ofsuccess, the vapor compression system cost rises dramatically as thecomplexity of the vapor compression system increases. Accordingly, aneed exists for an efficient vapor compression system that can beinstalled at low cost and operated at high efficiency.

BRIEF SUMMARY

According to a first aspect of the present invention, a vaporcompression system is provided that maintains high operating efficiencyby feeding a saturated vapor into the inlet of an evaporator. As usedherein, the term “saturated vapor” refers to a heat transfer fluid thatresides in both a liquid state and a vapor state with matched enthalpy,indicating the pressure and temperature of the heat transfer fluid arein correlation with each other. Saturated vapor is a high quality liquidvapor mixture. By feeding saturated vapor to the evaporator, heattransfer fluid in both a liquid and a vapor state enters the evaporatorcoils. Thus, the heat transfer fluid is delivered to the evaporator in aphysical state in which maximum heat can be absorbed by the fluid. Inaddition to high efficiency operation of the evaporator, in onepreferred embodiment of the invention, the vapor compression systemprovides a simple means of defrosting the evaporator. A multifunctionalvalve is employed that contains separate passageways feeding into acommon chamber. In operation, the multifunctional valve can transfereither a saturated vapor, for cooling, or a high temperature vapor, fordefrosting, to the evaporator.

In one form, the vapor compression system includes an evaporator forevaporating a heat transfer fluid, a compressor for compressing the heattransfer fluid to a relatively high temperature and pressure, and acondenser for condensing the heat transfer fluid. A saturated vapor lineis coupled from an expansion valve to the evaporator. In one aspect ofthe invention, the diameter and the length of the saturated vapor lineis sufficient to insure substantial conversion of the heat transferfluid into a saturated vapor prior to delivery of the fluid to theevaporator. In one preferred embodiment of the invention, a heat sourceis applied to the heat transfer fluid in the saturated vapor linesufficient to vaporize a portion of the heat transfer fluid before theheat transfer fluid enters the evaporator. In one aspect of theinvention, a heat source is applied to the heat transfer fluid after theheat transfer fluid passes through the expansion valve and before theheat transfer fluid enters the evaporator. The heat source converts theheat transfer fluid from a low quality liquid vapor mixture to a highquality liquid vapor mixture, or a saturated vapor. Typically, at leastabout 5% of the heat transfer fluid is vaporized before entering theevaporator.

In one embodiment of the invention, the expansion valve resides within amultifunctional valve that includes a first inlet for receiving the heattransfer fluid in the liquid state, and a second inlet for receiving theheat transfer fluid in the vapor state. The multifunctional valvefurther includes passageways coupling the first and second inlets to acommon chamber. Gate valves positioned within the passageways enable theflow of heat transfer fluid to be independently interrupted in eachpassageway. The ability to independently control the flow of saturatedvapor and high temperature vapor through the vapor compression systemproduces high operating efficiency by both increased heat transfer ratesat the evaporator and by rapid defrosting of the evaporator. Theincreased operating efficiency enables the vapor compression system tobe charged with relatively small amounts of heat transfer fluid, yet thevapor compression system can handle relatively large thermal loads.

In yet another embodiment, heat transfer fluid enters the common chamberof the multifunctional valve as a liquid vapor mixture and generallyfollows a flow direction. By controlling the flow rate of the heattransfer fluid and the shape of the common chamber, its is possible toseparate a substantial amount of the liquid vapor mixture into liquidand vapor so that heat transfer fluid exists the common chamber throughan outlet as liquid and vapor, wherein a substantial amount of theliquid is separate and apart from a substantial amount of the vapor.

In one embodiment, the vapor compression system includes a compressor, acondenser, an evaporator, an XDX valve, and an expansion valve. Inaccordance with this embodiment, the flow of heat transfer fluid fromthe condenser to the evaporator can be switched to go through either theXDX valve or the expansion valve. Preferably, the vapor compressionsystem includes a sensor that measures the conditions of ambientsurroundings, that is, the area or space in which the conditions such astemperature and humidity are controlled or altered by vapor compressionsystem. Upon determining the conditions of the ambient surroundings, thesensor then decides whether to direct the flow of heat transfer fluid toeither the XDX valve or the expansion valve.

Another aspect of the invention provides a method of operating a vaporcompression system, comprising: compressing a heat transfer fluid in acompressor; condensing the heat transfer fluid in a condenser; expandingthe heat transfer fluid in an expansion device to form an expanded heattransfer fluid and supplying the expanded heat transfer fluid to anevaporator feed line, at least one of the expansion device, a diameterof the evaporator feed line, and a length of the evaporator feed lineconverting a significant amount of a liquid form of the expanded liquidheat transfer fluid to a high quality liquid vapor mixture; supplyingthe high quality liquid vapor mixture to an evaporator coil having aheat transfer surface, converting a portion of a liquid form of the highquality liquid vapor mixture to a vapor form within the evaporator coil;and returning the heat transfer fluid to the compressor.

In one embodiment of this aspect, at a fixed cooling load, the heattransfer surface of the evaporator coil is smaller than that required toobtain an equivalent evaporator capacity when the significant amount ofthe liquid heat transfer fluid is not converted from a liquid form to ahigh quality liquid vapor mixture.

In another embodiment of this aspect, at a fixed cooling load, theconversion of the significant amount of the liquid refrigerant from aliquid form to a high quality liquid vapor mixture allows for at leastan equivalent evaporator capacity to be achieved using an decreased heattransfer fluid load when compared to the heat transfer fluid loadrequired when the significant amount of the liquid heat transfer fluidis not converted from a liquid form to a high quality liquid vapormixture.

In another embodiment of this aspect, operating at a fixed cooling load,the conversion of the significant amount of the liquid heat transferfluid from a liquid form to a high quality liquid vapor mixture allowsfor at least an equivalent evaporator capacity to that achieved when thesignificant amount of the liquid heat transfer fluid is not convertedfrom a liquid form to a high quality liquid vapor mixture and wherein adistributor is present between the evaporator feed line and theevaporator coil.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of a vapor-compression system arranged inaccordance with one embodiment of the invention;

FIG. 2 is a side view, in partial cross-section, of a first side of amultifunctional valve in accordance with one embodiment of theinvention;

FIG. 3 is a side view, in partial cross-section, of a second side of themultifunctional valve illustrated in FIG. 2;

FIG. 4 is an exploded view of a multifunctional valve in accordance withone embodiment of the invention;

FIG. 5 is a schematic view of a vapor-compression system in accordancewith another embodiment of the invention;

FIG. 6 is an exploded view of the multifunctional valve in accordancewith another embodiment of the invention;

FIG. 7 is a schematic view of a vapor-compression system in accordancewith yet another embodiment of the invention;

FIG. 8 is an enlarged cross-sectional view of a portion of the vaporcompression system illustrated in FIG. 7;

FIG. 9 is a schematic view, in partial cross-section, of a recoveryvalve in accordance with one embodiment of this invention;

FIG. 10 is a schematic view, in partial cross-section, of a recoveryvalve in accordance with yet another embodiment of this invention;

FIG. 11 is a plan view, partially in section, of a valve body for amultifunctional valve in accordance with a further embodiment of thepresent invention;

FIG. 12 is a side elevational view of the valve body for themultifunctional valve shown in FIG. 11;

FIG. 13 is an exploded view, partially in section, of themultifunctional valve shown in FIGS. 11 and 12;

FIG. 14 is an enlarged view of a portion of the multifunctional valveshown in FIG. 12;

FIG. 15 is a plan view, partially in section, of a valve body for amultifunctional valve in accordance with a further embodiment of thepresent invention;

FIG. 16. is a schematic drawing of a vapor-compression system arrangedin accordance with another embodiment of the invention;

FIG. 17 is a cross sectional view of a valve body for a multifunctionalvalve in accordance with a further embodiment of the present invention;

FIG. 18 is a cross sectional view of a valve body for a multifunctionalvalve in accordance with a further embodiment of the present invention;

FIG. 19 is a cross sectional view of a valve body for a multifunctionalvalve in accordance with a further embodiment of the present invention;

FIG. 20 is a schematic drawing of a vapor-compression system arranged inaccordance with another embodiment of the invention;

FIG. 21 is a side view of a fast-action capillary tube in accordancewith a further embodiment of the present invention; and

FIG. 22 is an enlarged cross-sectional view of a portion of the vaporcompression in accordance with another embodiment of the invention.

FIG. 23 is a schematic drawing illustrating three manifoldconfigurations: (a) an up-feed manifold; (b) a down-feed manifold; and(c) a side-feed manifold.

FIG. 24 is a schematic drawing illustrating the delivery of expandedheat transfer fluid from an expansion device to a multi-circuitevaporator coil via a distributor nozzle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of a vapor-compression system 10 arranged in accordancewith one embodiment of the invention is illustrated in FIG. 1. Vaporcompression system 10 includes a compressor 12, a condenser 14, anevaporator 16, and a multifunctional valve 18. Compressor 12 is coupledto condenser 14 by a discharge line 20. Multifunctional valve 18 iscoupled to condenser 14 by a liquid line coupled to a first inlet 24 ofmultifunctional valve 18. Additionally, multifunctional valve 18 iscoupled to discharge line 20 at a second inlet 26. A saturated vaporline 28 couples multifunctional valve 18 to evaporator 16, and a suctionline 30 couples the outlet of evaporator 16 to the inlet of compressor12. A temperature sensor 32 is mounted to suction line 30 and isoperably connected to multifunctional valve 18. In accordance with theinvention, compressor 12, condenser 14, multifunctional valve 18 andtemperature sensor 32 are located within a control unit 34.Correspondingly, evaporator 16 is located within a refrigeration case36. In one preferred embodiment of the invention, compressor 12,condenser 14, multifunctional valve 18, temperature sensor 32 andevaporator 16 are all located within a refrigeration case 36. In anotherpreferred embodiment of the invention, the vapor compression systemcomprises control unit 34 and refrigeration case 36, wherein compressor12 and condenser 14 are located within the control unit 34, and whereinevaporator 16, multifunctional valve 18, and temperature sensor 32 arelocated within refrigeration case 36.

The vapor compression system of the present invention can utilizeessentially any commercially available heat transfer fluid includingrefrigerants such as, for example, chlorofluorocarbons such as R-12which is a dicholordifluoromethane, R-22 which is amonochlorodifluoromethane, R-500 which is an azeotropic refrigerantconsisting of R-12 and R-152a, R-503 which is an azeotropic refrigerantconsisting of R-23 and R-13, and R-502 which is an azeotropicrefrigerant consisting of R-22 and R-115. The vapor compression systemof the present invention can also utilize refrigerants such as, but notlimited to refrigerants R-13, R-113, 141b, 123a, 123, R-114, and R-11.Additionally, the vapor compression system of the present invention canutilize refrigerants such as, for example, hydrochlorofluorocarbons suchas 141b, 123a, 123, and 124, hydrofluorocarbons such as R-134a, 134,152, 143a, 125, 32, 23, and azeotropic HFCs such as AZ-20 and AZ-50(which is commonly known as R-507). Blended refrigerants such as MP-39,HP-80, FC-14, R-717, and HP-62 (commonly known as R-404a), may also beused as refrigerants in the vapor compression system of the presentinvention. Accordingly, it should be appreciated that the particularrefrigerant or combination of refrigerants utilized in the presentinvention is not deemed to be critical to the operation of the presentinvention since this invention is expected to operate with a greatersystem efficiency with virtually all refrigerants than is achievable byany previously known vapor compression system utilizing the samerefrigerant.

In operation, compressor 12 compresses the heat transfer fluid, to arelatively high pressure and temperature. The temperature and pressureto which the heat transfer fluid is compressed by compressor 12 willdepend upon the particular size of vapor compression system 10 and thecooling load requirements of the vapor compression system. Compressor 12pumps the heat transfer fluid into discharge line 20 and into condenser14. As will be described in more detail below, during coolingoperations, second inlet 26 is closed and the entire output ofcompressor 12 is pumped through condenser 14.

In condenser 14, a medium such as air, water, or a secondary refrigerantis blown past coils within condenser 14 causing the pressurized heattransfer fluid to change to the liquid state. The temperature of theheat transfer fluid drops about 10 to 40° F. (5.6 to 22.2° C.),depending on the particular heat transfer fluid, or glycol, or the like,as the latent heat within the fluid is expelled during the condensationprocess. Condenser 14 discharges the liquefied heat transfer fluid toliquid line 22. As shown in FIG. 1, liquid line 22 immediatelydischarges into multifunctional valve 18. Because liquid line 22 isrelatively short, the pressurized liquid carried by liquid line 22 doesnot substantially increase in temperature as it passes from condenser 14to multifunctional valve 18. By configuring vapor compression system 10to have a short liquid line 22, vapor compression system 10advantageously delivers substantial amounts of heat transfer fluid tomultifunctional valve 18 at a low temperature and high pressure. Sincethe heat transfer fluid does not travel a great distance once it isconverted to a high-pressure liquid, little heat absorbing capability islost by the inadvertent warming of the liquid before it entersmultifunctional valve 18, or by a loss in liquid pressure. While in theabove embodiments of the invention, the vapor compression system uses arelatively short liquid line 22, it is possible to implement theadvantages of the present invention in a vapor compression system usinga relatively long liquid line 22, as will be described below. The heattransfer fluid discharged by condenser 14 enters multifunctional valve18 at first inlet 24 and undergoes a volumetric expansion at a ratedetermined by the temperature of suction line 30 at temperature sensor32. Multifunctional valve 18 discharges the heat transfer fluid as asaturated vapor into saturated vapor line 28. Temperature sensor 32relays temperature information through a control line 33 tomultifunctional valve 18.

Those skilled in the art will recognize that vapor compression system 10can be used in a wide variety of applications for controlling thetemperature of an enclosure, such as a refrigeration case in whichperishable food items are stored. For example, where vapor compressionsystem 10 is employed to control the temperature of a refrigeration casehaving a cooling load of about 12000 Btu/hr (84 g cal/s), compressor 12discharges about 3 to 5 lbs/min (1.36 to 2.27 kg/min) of R-12 at atemperature of about 110° F. (43.3° C.) to about 120° F. (48.9° C.) anda pressure of about 150 lbs/in² (1.03 E5 N/m²) to about 180 lbs/in.²(1.25 E5 N/m²)

In accordance with one preferred embodiment of the invention, saturatedvapor line 28 is sized in such a way that the low pressure fluiddischarged into saturated vapor line 28 substantially converts to asaturated vapor as it travels through saturated vapor line 28. In oneembodiment, saturated vapor line 28 is sized to handle about 2500 ft/min(76 m/min) to 3700 ft/min (1128 m/min) of a heat transfer fluid, such asR-12, and the like, and has a diameter of about 0.5 to 1.0 inches (1.27to 2.54 cm), and a length of about 90 to 100 feet (27 to 30.5 m). Asdescribed in more detail below, multifunctional valve 18 includes acommon chamber immediately before the outlet. The heat transfer fluidundergoes an additional volumetric expansion as it enters the commonchamber. The additional volumetric expansion of the heat transfer fluidin the common chamber of multifunctional valve 18 is equivalent to aneffective increase in the line size of saturated vapor line 28 by about225%.

Those skilled in the art will further recognize that the positioning ofa valve for volumetrically expanding of the heat transfer fluid in closeproximity to the condenser, and the relatively great length of the fluidline between the point of volumetric expansion and the evaporator,differs considerably from systems of the prior art. In a typical priorart system, an expansion valve is positioned immediately adjacent to theinlet of the evaporator, and if a temperature sensing device is used,the device is mounted in close proximity to the outlet of theevaporator. As previously described, such system can suffer from poorefficiency because substantial amounts of the evaporator carry a liquidrather than a saturated vapor. Fluctuations in high side pressure,liquid temperature, heat load or other conditions can adversely effectthe evaporator's efficiency.

In contrast to the prior art, the inventive vapor compression systemdescribed herein positions a saturated vapor line between the point ofvolumetric expansion and the inlet of the evaporator, such that portionsof the heat transfer fluid are converted to a saturated vapor before theheat transfer fluid enters the evaporator. By charging evaporator 16with a saturated vapor, the cooling efficiency is greatly increased. Byincreasing the cooling efficiency of an evaporator, such as evaporator16, numerous benefits are realized by the vapor compression system. Forexample, less heat transfer fluid is needed to control the airtemperature of refrigeration case 36 at a desired level. Additionally,less electricity is needed to power compressor 12 resulting in loweroperating cost. Further, compressor 12 can be sized smaller than a priorart system operating to handle a similar cooling load. Moreover, in onepreferred embodiment of the invention, the vapor compression systemavoids placing numerous components in proximity to the evaporator. Byrestricting the placement of components within refrigeration case 36 toa minimal number, the thermal loading of refrigeration case 36 isminimized.

While in the above embodiments of the invention, multifunctional valve18 is positioned in close proximity to condenser 14, thus creating arelatively short liquid line 22 and a relatively long saturated vaporline 28, it is possible to implement the advantages of the presentinvention even if multifunctional valve 18 is positioned immediatelyadjacent to the inlet of the evaporator 16, thus creating a relativelylong liquid line 22 and a relatively short saturated vapor line 28. Forexample, in one preferred embodiment of the invention, multifunctionalvalve 18 is positioned immediately adjacent to the inlet of theevaporator 16, thus creating a relatively long liquid line 22 and arelatively short saturated vapor line 28, as illustrated in FIG. 7. Inorder to insure that the heat transfer fluid entering evaporator 16 is asaturated vapor, a heat source 25 is applied to saturated vapor line 28,as illustrated in FIGS. 7-8. Temperature sensor 32 is mounted to suctionline 30 and operatively connected to multifunctional valve 18, whereinheat source 25 is of sufficient intensity so as to vaporize a portion ofthe heat transfer fluid before the heat transfer fluid enters evaporator16. The heat transfer fluid entering evaporator 16 is converted to asaturated vapor wherein a portion of the heat transfer fluids exists ina liquid state 29, and another portion of the heat transfer fluid existsin a vapor state 31, as illustrated in FIG. 8.

Preferably heat source 25 used to vaporize a portion of the heattransfer fluid comprises heat transferred to the ambient surroundingsfrom condenser 14, however, heat source 25 can comprise any external orinternal source of heat known to one of ordinary skill in the art, suchas, for example, heat transferred to the ambient surroundings from thedischarge line 20, heat transferred to the ambient surroundings from acompressor, heat generated by a compressor, heat generated from anelectrical heat source, heat generated using combustible materials, heatgenerated using solar energy, or any other source of heat. Heat source25 can also comprise an active heat source, that is, any heat sourcethat is intentionally applied to a part of vapor compression system 10,such as saturated vapor line 28. An active heat source includes but isnot limited to a source of heat such as heat generated from anelectrical heat source, heat generated using combustible materials, heatgenerated using solar energy, or any other source of heat which isintentionally and actively applied to any part of vapor compressionsystem 10. A heat source that comprises heat which accidentally leaksinto any part of vapor compression system 10 or heat which isunintentionally or unknowingly absorbed into any part of vaporcompression system 10, either due to poor insulation or other reasons,is not an active heat source.

In one preferred embodiment of the invention, temperature sensor 32monitors the heat transfer fluid exiting evaporator 16 in order toinsure that a portion of the heat transfer fluid is in a liquid state 29upon exiting evaporator 16, as illustrated in FIG. 8. In one preferredembodiment of the invention, at least about 5% of the of the heattransfer fluid is vaporized before the heat transfer fluid enters theevaporator, and at least about 1% of the heat transfer fluid is in aliquid state upon exiting the evaporator. By insuring that a portion ofthe heat transfer fluid is in liquid state 29 and vapor state 31 uponentering and exiting the evaporator, the vapor compression system of thepresent invention allows evaporator 16 to operate with maximumefficiency. In one preferred embodiment of the invention, the heattransfer fluid is in at least about a 1% superheated state upon exitingevaporator 16. In one preferred embodiment of the invention, the heattransfer fluid is between about a 1% liquid state and about a 1%superheated vapor state upon exiting evaporator 16.

While the above embodiments rely on heat source 25 or the dimensions andlength of saturated vapor line 28 to insure that the heat transfer fluidenters the evaporator 16 as a saturated vapor, any means known to one ofordinary skill in the art which can convert the heat transfer fluid to asaturated vapor upon entering evaporator 16 can be used. Additionally,while the above embodiments use temperature sensor 32 to monitor thestate of the heat transfer fluid exiting the evaporator, any meteringdevice known to one of ordinary skill in the art which can determine thestate of the heat transfer fluid upon exiting the evaporator can beused, such as a pressure sensor, or a sensor which measures the densityof the fluid. Additionally, while in the above embodiments, the meteringdevice monitors the state of the heat transfer fluid exiting evaporator16, the metering device can also be placed at any point in or aroundevaporator 16 to monitor the state of the heat transfer fluid at anypoint in or around evaporator 16.

Shown in FIG. 2 is a side view, in partial cross-section, of oneembodiment of multifunctional valve 18. Heat transfer fluid enters firstinlet 24 and traverses a first passageway 38 to a common chamber 40. Anexpansion valve 42 is positioned in first passageway 38 near first inlet24. Expansion valve 42 meters the flow of the heat transfer fluidthrough first passageway 38 by means of a diaphragm (not shown) enclosedwithin an upper valve housing 44. Expansion valve 42 can be any meteringunit known to one of ordinary skill in the art that can be used to meterthe flow of heat transfer fluid, such as a thermostatic expansion valve,a capillary tube, or a pressure control. In one preferred embodiment,expansion valve 42 is a fast-action capillary tube 500, as illustratedin FIG. 21. Fast-action capillary tube 500 includes an inlet 505, anoutlet 510, an expansion line 515, and a gating valve 520. Heat transferfluid enters fast-action capillary tube 500 at inlet 505 and passesthrough expansion line 515. Expansion line 515 is sized with a lengthand diameter such that heat transfer fluid is allowed to expand withinexpansion line 515. In one preferred embodiment, heat transfer fluidenter expansion line 515 as a liquid and expansion line 515 is sizedsuch that heat transfer fluid expands from a liquid to a low qualityliquid vapor mixture. Preferably, heat transfer fluid expands from aliquid to a high quality liquid vapor mixture within expansion line 515.Upon passing through expansion line 515, heat transfer fluid exitsfast-action capillary tube 500 at outlet 510. Gating valve 520 iscoupled to outlet 510 and control the flow of heat transfer fluidthrough fast-action capillary tube 500. Preferably, gating valve 520 isa solenoid valve capable of terminating the flow of heat transfer fluidthrough a passageway, such as expansion line 515, in response to anelectrical signal. However, gating valve 520 may be any valve capable ofterminating the flow of heat transfer fluid through a passageway knownto one of ordinary skill, such as a valve that is mechanicallyactivated.

When a vapor compression system, such as vapor compression system 10, isin operation, heat transfer fluid is pumped through fast-actioncapillary tube 500 from inlet 505 to outlet 510, and gating valve 520 isopened to allow heat transfer fluid to exit from fast-action capillarytube 500. When a vapor compression system has ceased operation, or hasbeen cycled off, gating valve 520 is closed to allow heat transfer fluidto fill up fast-action capillary tube 500. By allowing fast-actioncapillary tube 500 to fill up with heat transfer fluid, fast-actioncapillary tube 500 is able to immediately supply a unit, such as anevaporator, with a rush of heat transfer fluid in a liquid state. Bybeing able to supply a unit, such as an evaporator, with a rush of heattransfer fluid in a liquid state, fast-action capillary tube 500 allowsa vapor compression system to cycle on, or begin operation, rapidly.

Control line 33 is connected to an input 62 located on upper valvehousing 44. Signals relayed through control line 33 activate thediaphragm within upper valve housing 44. The diaphragm actuates a valveassembly 54 (shown in FIG. 4) to control the amount of heat transferfluid entering an expansion chamber 52 (shown in FIG. 4) from firstinlet 24. A gating valve 46 is positioned in first passageway 38 nearcommon chamber 40. In a preferred embodiment of the invention, gatingvalve 46 is a solenoid valve capable of terminating the flow of heattransfer fluid through first passageway 38 in response to an electricalsignal.

Shown in FIG. 3 is a side view, in partial cross-section, of a secondside of multifunctional valve 18. A second passageway 48 couples secondinlet 26 to common chamber 40. A gating valve 50 is positioned in secondpassageway 48 near common chamber 40. In a preferred embodiment of theinvention, gating valve 50 is a solenoid valve capable of terminatingthe flow of heat transfer fluid through second passageway 48 uponreceiving an electrical signal. Common chamber 40 discharges the heattransfer fluid from multifunctional valve 18 through an outlet 41.

An exploded perspective view of multifunctional valve 18 is illustratedin FIG. 4. Expansion valve 42 is seen to include expansion chamber 52adjacent first inlet 24, valve assembly 54, and upper valve housing 44.Valve assembly 54 is actuated by a diaphragm (not shown) containedwithin the upper valve housing 44. First and second tubes 56 and 58 arelocated intermediate to expansion chamber 52 and a valve body 60. Gatingvalves 46 and 50 are mounted on valve body 60. In accordance with theinvention, vapor compression system 10 can be operated in a defrost modeby closing gating valve 46 and opening gating valve 50. In defrost mode,high temperature heat transfer fluid enters second inlet 26 andtraverses second passageway 48 and enters common chamber 40. The hightemperature vapors are discharged through outlet 41 and traversesaturated vapor line 28 to evaporator 16. The high temperature vapor hasa temperature sufficient to raise the temperature of evaporator 16 byabout 50 to 120° F. (27.8 to 66.7° C.). The temperature rise issufficient to remove frost from evaporator 16 and restore the heattransfer rate to desired operational levels.

While the above embodiments use a multifunctional valve 18 for expandingthe heat transfer fluid before entering evaporator 16, any thermostaticexpansion valve or throttling valve, such as expansion valve 42 or evenrecovery valve 19, may be used to expand heat transfer fluid beforeentering evaporator 16.

In one preferred embodiment of the invention heat source 25 is appliedto the heat transfer fluid after the heat transfer fluid passes throughexpansion valve 42 and before the heat transfer fluid enters the inletof evaporator 16 to convert the heat transfer fluid from a low qualityliquid vapor mixture to a high quality liquid vapor mixture, or asaturated vapor. In one preferred embodiment of the invention, heatsource 25 is applied to a multifunctional valve 18. In another preferredembodiment of the invention heat source 25 is applied within recoveryvalve 19, as illustrated in FIG. 9. Recovery valve 19 comprises a firstinlet 124 connected to liquid line 22 and a first outlet 159 connectedto saturated vapor line 28. Heat transfer fluid enters first inlet 124of recovery valve 19 to a common chamber 140. An expansion valve 142 ispositioned near first inlet 124 to expand the heat transfer fluidentering first inlet 124 from a liquid state to a low quality liquidvapor mixture. Second inlet 127 is connected to discharge line 20, andreceives high temperature heat transfer fluid exiting compressor 12.High temperature heat transfer fluid exiting compressor 12 enters secondinlet 127 and traverses second passageway 123. Second passageway 123 isconnected to second inlet 127 and second outlet 130. A portion of secondpassageway 123 is located adjacent to common chamber 140.

As the high temperature heat transfer fluid nears common chamber 140,heat from the high temperature heat transfer fluid is transferred fromthe second passageway 123 to the common chamber 140 in the form of heatsource 125. By applying heat from heat source 125 to the heat transferfluid in common chamber 140, the heat transfer fluid in common chamber140 is converted from a low quality liquid vapor mixture to a highquality liquid vapor mixture, or saturated vapor, as the heat transferfluid flows through common chamber 140. Additionally, the hightemperature heat transfer fluid in the second passageway 123 is cooledas the high temperature heat transfer fluid passes near common chamber140. Upon traversing second passageway 123, the cooled high temperatureheat transfer fluid exits second outlet 130 and enters condenser 14.Heat transfer fluid in common chamber 140 exits recovery valve 19 atfirst outlet 159 into saturated vapor line 28 as a high quality liquidvapor mixture, or saturated vapor.

While in the above preferred embodiment, heat source 125 comprises heattransferred to the ambient surroundings from a compressor, heat source125 may comprise any external or internal source of heat known to one ofordinary skill in the art, such as, for example, heat generated from anelectrical heat source, heat generated using combustible materials, heatgenerated using solar energy, or any other source of heat. Heat source125 can also comprise any heat source 25 and any active heat source, aspreviously defined.

In one preferred embodiment of the invention, recovery valve 19comprises third passageway 148 and third inlet 126. Third inlet 126 isconnected to discharge line 20, and receives high temperature heattransfer fluid exiting compressor 12. A first gating valve (not shown)capable of terminating the flow of heat transfer fluid through commonchamber 140 is positioned near the first inlet 124 of common chamber140. Third passageway 148 connects third inlet 126 to common chamber140. A second gating valve (not shown) is positioned in third passageway148 near common chamber 140. In a preferred embodiment of the invention,the second gating valve is a solenoid valve capable of terminating theflow of heat transfer fluid through third passageway 148 upon receivingan electrical signal.

In accordance with the invention, vapor compression system 10 can beoperated in a defrost mode by closing the first gating valve locatednear first inlet 124 of common chamber 140 and opening the second gatingvalve positioned in third passageway 148 near common chamber 140. Indefrost mode, high temperature heat transfer fluid from compressor 12enters third inlet 126 and traverses third passageway 148 and enterscommon chamber 140. The high temperature heat transfer fluid isdischarged through first outlet 159 of recovery valve 19 and traversessaturated vapor line 28 to evaporator 16. The high temperature heattransfer fluid has a temperature sufficient to raise the temperature ofevaporator 16 by about 50 to 120° F. (27.8 to 66.7° C.). The temperaturerise is sufficient to remove frost from evaporator 16 and restore theheat transfer rate to desired operational levels.

During the defrost cycle, any pockets of oil trapped in the vaporcompression system will be warmed and carried in the same direction offlow as the heat transfer fluid. By forcing hot gas through the vaporcompression system in a forward flow direction, the trapped oil willeventually be returned to the compressor. The hot gas will travelthrough the vapor compression system at a relatively high velocity,giving the gas less time to cool thereby improving the defrostingefficiency. The forward flow defrost method of the invention offersnumerous advantages to a reverse flow defrost method. For example,reverse flow defrost systems employ a small diameter check valve nearthe inlet of the evaporator. The check valve restricts the flow of hotgas in the reverse direction reducing its velocity and hence itsdefrosting efficiency. Furthermore, the forward flow defrost method ofthe invention avoids pressure build up in the vapor compression systemduring the defrost system. Additionally, reverse flow methods tend topush oil trapped in the vapor compression system back into the expansionvalve. This is not desirable because excess oil in the expansion valvecan cause gumming that restricts the operation of the expansion valve.Also, with forward defrost, the liquid line pressure is not reduced inany additional refrigeration circuits being operated in addition to thedefrost circuit.

It will be apparent to those skilled in the art that a vapor compressionsystem arranged in accordance with the invention can be operated withless heat transfer fluid those comparable sized system of the prior art.By locating the multifunctional valve near the condenser, rather thannear the evaporation, the saturated vapor line is filled with arelatively low-density vapor, rather than a relatively high-densityliquid. Alternatively, by applying a heat source to the saturated vaporline, the saturated vapor line is also filled with a relativelylow-density vapor, rather than a relatively high-density liquid.Additionally, prior art systems compensate for low temperature ambientoperations (e.g. winter time) by flooding the evaporator in order toreinforce a proper head pressure at the expansion valve. In onepreferred embodiment of the invention, vapor compression system heatpressure is more readily maintained in cold weather, since themultifunctional valve is positioned in close proximity to the condenser.

The forward flow defrost capability of the invention also offersnumerous operating benefits as a result of improved defrostingefficiency. For example, by forcing trapped oil back into thecompressor, liquid slugging is avoided, which has the effect ofincreasing the useful life of the equipment. Furthermore, reducedoperating cost are realized because less time is required to defrost thevapor compression system. Since the flow of hot gas can be quicklyterminated, the vapor compression system can be rapidly returned tonormal cooling operation. When frost is removed from evaporator 16,temperature sensor 32 detects a temperature increase in the heattransfer fluid in suction line 30. When the temperature rises to a givenset point, gating valve 50 and multifunctional valve 18 is closed. Oncethe flow of heat transfer fluid through first passageway 38 resumes,cold saturated vapor quickly returns to evaporator 16 to resumerefrigeration operation.

Those skilled in the art will appreciate that numerous modifications canbe made to enable the vapor compression system of the invention toaddress a variety of applications. For example, vapor compressionsystems operating in retail food outlets typically include a number ofrefrigeration cases that can be serviced by a common compressor system.Also, in applications requiring refrigeration operations with highthermal loads, multiple compressors can be used to increase the coolingcapacity of the vapor compression system.

A vapor compression system 64 in accordance with another embodiment ofthe invention having multiple evaporators and multiple compressors isillustrated in FIG. 5. In keeping with the operating efficiency andlow-cost advantages of the invention, the multiple compressors, thecondenser, and the multiple multifunctional valves are contained withina control unit 66. Saturated vapor lines 68 and 70 feed saturated vaporfrom control unit 66 to evaporators 72 and 74, respectively. Evaporator72 is located in a first refrigeration case 76, and evaporator 74 islocated in a second refrigeration case 78. First and secondrefrigeration cases 76 and 78 can be located adjacent to each other, oralternatively, at relatively great distance from each other. The exactlocation will depend upon the particular application. For example, in aretail food outlet, refrigeration cases are typically placed adjacent toeach other along an isle way. Importantly, the vapor compression systemof the invention is adaptable to a wide variety of operatingenvironments. This advantage is obtained, in part, because the number ofcomponents within each refrigeration case is minimal. In one preferredembodiment of the invention, by avoiding the requirement of placingnumerous system components in proximity to the evaporator, the vaporcompression system can be used where space is at a minimum. This isespecially advantageous to retail store operations, where floor space isoften limited.

In operation, multiple compressors 80 feed heat transfer fluid into anoutput manifold 82 that is connected to a discharge line 84. Dischargeline 84 feeds a condenser 86 and has a first branch line 88 feeding afirst multifunctional valve 90 and a second branch line 92 feeding asecond multifunctional valve 94. A bifurcated liquid line 96 feeds heattransfer fluid from condenser 86 to first and second multifunctionalvalves 90 and 94. Saturated vapor line 68 couples first multifunctionalvalve 90 with evaporator 72, and saturated vapor line 70 couples secondmultifunctional valve 94 with evaporator 74. A bifurcated suction line98 couples evaporators 72 and 74 to a collector manifold 100 feedingmultiple compressors 80. A temperature sensor 102 is located on a firstsegment 104 of bifurcated suction line 98 and relays signals to firstmultifunctional valve 90. A temperature sensor 106 is located on asecond segment 108 of bifurcated suction line 98 and relays signals tosecond multifunctional valve 94. In one preferred embodiment of theinvention, a heat source, such as heat source 25, can be applied tosaturated vapor lines 68 and 70 to insure that the heat transfer fluidenters evaporators 72 and 74 as a saturated vapor.

Those skilled in the art will appreciate that numerous modifications andvariations of vapor compression system 64 can be made to addressdifferent refrigeration applications. For example, more than twoevaporators can be added to the vapor compression system in accordancewith the general method illustrated in FIG. 5. Additionally, morecondensers and more compressors can also be included in the vaporcompression system to further increase the cooling capability.

A multifunctional valve 110 arranged in accordance with anotherembodiment of the invention is illustrated in FIG. 6. In similarity withthe previous multifunctional valve embodiment, the heat transfer fluidexiting the condenser in the liquid state enters a first inlet 122 andexpands in expansion chamber 152. The flow of heat transfer fluid ismetered by valve assembly 154. In the present embodiment, a solenoidvalve 112 has an armature 114 extending into a common seating area 116.In refrigeration mode, armature 114 extends to the bottom of commonseating area 116 and cold refrigerant flows through a passageway 118 toa common chamber 140, then to an outlet 120. In defrost mode, hot vaporenters second inlet 126 and travels through common seating area 116 tocommon chamber 140, then to outlet 120. Multifunctional valve 110includes a reduced number of components, because the design is such asto allow a single gating valve to control the flow of hot vapor and coldvapor through the multifunctional valve 110.

In yet another embodiment of the invention, the flow of liquefied heattransfer fluid from the liquid line through the multifunctional valvecan be controlled by a check valve positioned in the first passageway togate the flow of the liquefied heat transfer fluid into the saturatedvapor line. The flow of heat transfer fluid through the vaporcompression system is controlled by a pressure valve located in thesuction line in proximity to the inlet of the compressor. Accordingly,the various functions of a multifunctional valve of the invention can beperformed by separate components positioned at different locationswithin the vapor compression system. All such variations andmodifications are contemplated by the present invention.

Those skilled in the art will recognize that the vapor compressionsystem and method described herein can be implemented in a variety ofconfigurations. For example, the compressor, condenser, multifunctionalvalve, and the evaporator can all be housed in a single unit and placedin a walk-in cooler. In this application, the condenser protrudesthrough the wall of the walk-in cooler and ambient air outside thecooler is used to condense the heat transfer fluid.

In another application, the vapor compression system and method of theinvention can be configured for air-conditioning a home or business. Inthis application, a defrost cycle is unnecessary since icing of theevaporator is usually not a problem.

In yet another application, the vapor compression system and method ofthe invention can be used to chill water. In this application, theevaporator is immersed in water to be chilled. Alternatively, water canbe pumped through tubes that are meshed with the evaporator coils.

In a further application, the vapor compression system and method of theinvention can be cascaded together with another system for achievingextremely low refrigeration temperatures. For example, two systems usingdifferent heat transfer fluids can be coupled together such that theevaporator of a first system provides a low temperature ambient. Acondenser of the second system is placed in the low temperature ambientand is used to condense the heat transfer fluid in the second system.

Another embodiment of a multifunctional valve 225 is shown in FIGS.11-14 and is generally designated by the reference numeral 225. Thisembodiment is functionally similar to that described in FIGS. 2-4 andFIG. 6 which was generally designated by the reference numeral 18. Asshown, this embodiment includes a main body or housing 226 whichpreferably is constructed as a single one-piece structure having a pairof threaded bosses 227, 228 that receive a pair of gating valves andcollar assemblies, one of which being shown in FIG. 13 and designated bythe reference numeral 229. This assembly includes a threaded collar 230,gasket 231 and solenoid-actuated gating valve receiving member 232having a central bore 233, that receives a reciprocally movable valvepin 234 that includes a spring 235 and needle valve element 236 which isreceived with a bore 237 of a valve seat member 238 having a resilientseal 239 that is sized to be sealingly received in well 240 of thehousing 226. A valve seat member 241 is snuggly received in a recess 242of valve seat member 238. Valve seat member 241 includes a bore 243 thatcooperates with needle valve element 236 to regulate the flow of heattransfer fluid therethrough.

A first inlet 244 (corresponding to first inlet 24 in the previouslydescribed embodiment) receives liquid feed heat transfer fluid fromexpansion valve 42, and a second inlet 245 (corresponding to secondinlet 26 of the previously described embodiment) receives hot gas fromthe compressor 12 during a defrost cycle. In one preferred embodimentmultifunctional valve 225 comprises first inlet 244, outlet 248, commonchamber 246, and expansion valve 42, as illustrated in FIG. F. In onepreferred embodiment, expansion valve 42 is connected with first inlet244. The valve body 226 includes a common chamber 246 (corresponding tocommon chamber 40 in the previously described embodiment). Expansionvalve 42 receives heat transfer fluid from the condenser 14 which thenpasses through inlet 244 into a semicircular well 247 which, when gatingvalve 229 is open, then passes into common chamber 246 and exits fromthe multifunctional valve 225 through outlet 248 (corresponding tooutlet 41 in the previously described embodiment).

A best shown in FIG. 11 the valve body 226 includes a first passageway249 (corresponding to first passageway 38 of the previously describedembodiment) which communicates first inlet 244 with common chamber 246.In like fashion, a second passageway 250 (corresponding to secondpassageway 48 of the previously described embodiment) communicatessecond inlet 245 with common chamber 246.

Insofar as operation of multifunctional valve 225 is concerned,reference is made to the previously described embodiment since thecomponents thereof function in the same way during the refrigeration anddefrost cycles. In one preferred embodiment, the heat transfer fluidexits the condenser 14 in the liquid state passes through expansionvalve 42. As the heat transfer fluid passes through expansion valve 42,the heat transfer fluid changes from a liquid to a liquid vapor mixture,wherein the heat transfer fluid is in both a liquid state and a vaporstate. The heat transfer fluid enters the first inlet 244 as a liquidvapor mixture and expands in common chamber 246.

In one preferred embodiment, the heat transfer fluid expands in adirection away from the general flow of the heat transfer fluid. As theheat transfer fluid expands in common chamber 246, the liquid separatesfrom the vapor in the heat transfer fluid. The heat transfer fluid thenexits common chamber 246. Preferably, the heat transfer fluid exitscommon chamber 246 as a liquid and a vapor, wherein a substantial amountof the liquid is separate and apart from a substantial amount of thevapor. The heat transfer fluid then passes through outlet 248 andtravels through saturated vapor line 28 to evaporator 16. In onepreferred embodiment, the heat transfer fluid then passes through outlet248 and enters evaporator 16 at first evaporative line 328, as describedin more detail below. Preferably, the heat transfer fluid travels fromoutlet 248 to the inlet of evaporator 16 as a liquid and a vapor,wherein a substantial amount of the liquid is separate and apart from asubstantial amount of the vapor.

In one preferred embodiment, a pair of gating valves 229 can be used tocontrol the flow of heat transfer fluid or hot vapor into common chamber246. In refrigeration mode, a first gating valve 229 is opened to allowheat transfer fluid to flow through first inlet 244 and into commonchamber 246, and then to outlet 248. In defrost mode, a second gatingvalve 229 is opened to allow hot vapor to flow through second inlet 245and into common chamber 246, and then to outlet 248. While in the aboveembodiments, multifunctional valve 225 has been described as havingmultiple gating valves 229, multifunctional valve 225 can be designedwith only one gating valve. Additionally, multifunctional valve 225 hasbeen described as having a second inlet 245 for allowing hot vapor toflow through during defrost mode, multifunctional valve 225 can bedesigned with only first inlet 244.

In one preferred embodiment, multifunctional valve 225 comprises bleedline 251, as illustrated in FIG. 15. Bleed line 251 is connected withcommon chamber 246 and allows heat transfer fluid that is in commonchamber 246 to travel to saturated vapor line 28 or first evaporativeline 328. In one preferred embodiment, bleed line 251 allows the liquidthat has separated from the liquid vapor mixture entering common chamber246 to travel to saturated vapor line 28 or first evaporative line 328.Preferably, bleed line 251 is connected to bottom surface 252 of commonchamber 246, wherein bottom surface 252 is the surface of common chamber246 located nearest the ground.

In one preferred embodiment, multifunctional valve 225 is dimensioned asspecified below in Table A and as illustrated in FIGS. 11-14. The lengthof common chamber 246 will be defined as the distance from outlet 248 toback wall 253. The length of common chamber 246 is represented by theletter G, as illustrated in FIG. 11. Common chamber 246 has a firstportion adjacent to a second portion, wherein the first portion beginsat outlet 248 and the second portion ends at back wall 253, asillustrated in FIG. 11. First inlet 244 and outlet 248 are bothconnected with the first portion. The heat transfer fluid enters commonchamber 246 through first inlet 244 and within the first portion of thecommon chamber 246. In one preferred embodiment, the first portion has alength equal to no more than about 75% of the length of common chamber246. More preferably, the first portion has a length equal to no morethan about 35% of the length of common chamber 246. TABLE A DIMENSIONSOF MULTIFUNCTIONAL VALVE Inches (all Millimeters dimensions notspecified (all dimensions not specified Dimensions are to be +/−0.015)are to be +/−0.381) A 2.500 63.5 B 2.125 53.975 C 1.718 43.637 D1(diameter) 0.812 20.625 D2 (diameter) 0.609 15.469 D3 (diameter) 1.68842.875 D4 (diameter) 1.312 (+/−0.002)  33.325 (+/−0.051) D5 (diameter)0.531 13.487 E 0.406 10.312 F 1.062 26.975 G 4.500 114.3 H 5.000 127 I0.781 19.837 J 2.500 63.5 K 1.250 31.75 L 0.466 11.836 M 0.812(+/−0.005) 20.6248 (+/−0.127) R1 (radius) 0.125 3.175

In one preferred embodiment, the heat transfer fluid enters commonchamber 246 through first inlet 244 as a low quality liquid vapormixture 270. Liquid vapor mixture 270 is in both a liquid state and avapor state, wherein the liquid is suspended within the vapor. As usedherein, the heat transfer fluid that is in a liquid state will bereferred to as liquid 280 and the heat transfer fluid that is in a vaporstate will be referred to as vapor 285. As the heat transfer fluidpasses from the inlet 244 of common chamber 246 to the outlet 248 ofcommon chamber 246, a portion of liquid 280 coalesces. As used herein,the term “coalesces” means to unite or to fuse together. Therefore, whenthe phrase “a portion of liquid 280 coalesces” is used, it is meant thata portion of liquid 280 becomes united with or fused together withanother portion of liquid 280. As the heat transfer fluid enters commonchamber 246, liquid 280 is arranged with liquid vapor mixture 270 asliquid droplets suspended in vapor 280. After the heat transfer fluidenters common chamber 246 as a liquid vapor mixture 270, the slowermoving liquid 280 begins to coalesce and settle at bottom surface 252 ofcommon chamber 246 while the faster moving vapor 285 is forced throughoutlet 248, as illustrated in FIGS. 17-19. By allowing liquid 280 tocoalesce and separate from vapor 285, heat is released from the liquidvapor mixture 270 allowing liquid 280 to cool off. The cooling off ofliquid 280 decreases the enthalpy of liquid vapor mixture 270,converting the heat transfer fluid in common chamber 246 from a lowquality liquid vapor mixture to a high quality liquid vapor mixture, ora saturated vapor.

In one preferred embodiment, as heat transfer fluid travels throughcommon chamber 246, a portion of liquid 280 within liquid vapor mixture270 coalesces into larger droplets which exit through outlet 248 alongwith vapor 285. In one preferred embodiment, the larger droplets ofliquid 280 coalesces into a stream of liquid 280, wherein the stream ofliquid 280 exits through outlet 248 along with a stream of vapor 285, asillustrated in FIGS. 17-19. Preferably, at least 10% of liquid 280coalesces into larger droplets of liquid 280 or a stream of liquid 280.More preferably, at least 35% of liquid 280 coalesces into largerdroplets of liquid 280 or a stream of liquid 280.

Common chamber 246 is divided into a first portion 290 and a secondportion 295. First portion 290 includes first inlet 244 and outlet 248.By including first inlet 244 and outlet 248, first portion is also theportion of common chamber 246 upon which heat transfer fluid must flowthrough upon entering common chamber 246, and therefore the portion ofcommon chamber 246 wherein flow direction 265 generally resides. Flowdirection 265 is the general direction the heat transfer fluid flows asthe heat transfer fluid travels from first inlet 244 to second inlet248, as illustrated by arrows in FIGS. 17-19. Second portion 295 islocated in common chamber 246 and allows for a portion of the heattransfer fluid to coalesce. Preferably, second portion 295 is locatedaway from flow direction 265, as illustrated in FIGS. 17-19. By locatingsecond portion 295 away from flow direction 265, the slower movingliquid 280 is allowed to accumulate in and coalesce in second portion295 and the faster moving vapor 285 is able to become separated fromliquid 280, as illustrated in FIGS. 17-19. Preferably, the heat transferfluid exists common chamber 246 through outlet 248 as a high qualityliquid vapor mixture, wherein liquid 280 has coalesced and issubstantially separate and apart from vapor 285, as illustrated in FIGS.17-19. Upon exiting common chamber 246 at outlet 248, the heat transferfluid then passes through saturated vapor line 28 to evaporator 16.

In one preferred embodiment, the flow of heat transfer fluid is in aturbulent state upon entering first inlet 244, so that a portion ofvapor 285 gets trapped in second portion 295, creating eddy 275 incommon chamber 246, and more preferably in second portion 295 of commonchamber 246. Eddy 275 is a current of heat transfer fluid that flows ina generally circular direction, as illustrated in FIGS. 17-19. Eddy 275helps liquid 280 to coalesce. In one preferred embodiment, the heattransfer fluid enters first inlet 244 in a turbulent state and createsat least one vortex 276 in common chamber 246, and more preferably insecond portion 295 of common chamber 246. Vortex 276, as defined herein,is a mass of heat transfer fluid having a whirling or circular motionthat forms a cavity or vacuum in the center of the circle and that drawstoward this cavity or vacuum bodies subject to this action. For example,when a vortex 276 is formed within common chamber 246, a cavity orvacuum forms in the center of vortex 276 that tends to draw vapor 285away from liquid vapor mixture 270. In this way, liquid 280 can beseparated from vapor 285 in liquid vapor mixture 270.

Common chamber 246 can comprise any one of a variety of geometricalconfigurations which allow a portion of liquid 280 to coalesce withincommon chamber 246 and separate from liquid 280. In one preferredembodiment, first inlet 244 is a distance N1 away from outlet 248 and adistance N2 from back wall 253, wherein the sum of N1 and N2 equals thelength of common chamber 246, as illustrated in FIG. 17. Preferably, N1is anywhere from about 5% to about 75% the length of common chamber 246.In one preferred embodiment, common chamber 246 includes reservoir 305located along bottom surface 252 of common chamber 246, as illustratedin FIG. 17. Reservoir 305 traps a portion of heat transfer fluid withincommon chamber 246, which causes liquid 280 to coalesce.

In one preferred embodiment, inlet 244 is adjacent with back wall 253and bottom surface 252 is located a distance N3 from outlet 248 and adistance N4 from inlet 244, as illustrated in FIGS. 18-19. N3 isanywhere from about 25% to about 95% the length of N4. In thisconfiguration, second portion 295 is able to trap a portion of heattransfer fluid within common chamber 246, which causes liquid 280 tocoalesce. In one preferred embodiment, common chamber 246 includes notch300 between first inlet 244 and outlet 248, as illustrated in FIG. 19.Notch 300 reduces the amount of heat transfer fluid that can exit commonchamber 246 through outlet 248. By reducing the amount of heat transferfluid that can exits common chamber 246, notch 300 encourages the fastermoving vapor 285 to separate from the slower moving liquid 280, whichcauses liquid 280 to coalesce. Preferably, notch 300 has a height N5 andoutlet 248 has a diameter N6, wherein N5 is anywhere from about 15% toabout 95% of N6. The embodiments of common chamber 246 discussed above,and as illustrated in FIGS. 17-19, are merely illustrative of theinvention and are not meant to limit the scope in any way whatsoever.

In one preferred embodiment, the flow rate upon which heat transferfluid is forced through first inlet 244 is increased to facilitate theseparation of liquid 280 from vapor 285 in liquid vapor mixture 270,which causes liquid 280 to coalesce. For example, in a vapor compressionsystem having a compressor of size X, a condenser of size Y, anevaporator of size Z, and first inlet 244 having a diameter of D, if theflow rate is increased from A to B, liquid 280 will more readilyseparate from vapor 285 and coalesce. Preferably, the flow rate of heattransfer fluid is increased so that the heat transfer fluid enteringcommon chamber 226 is in a turbulent flow. More preferably, the flowrate of heat transfer fluid is increased so that the heat transfer fluidentering common chamber 246 is at such a rate that Eddy 275 forms withincommon chamber 246, as illustrated in FIGS. 17-19. In one preferredembodiment, the heat transfer fluid passes through expansion valve 42and then enters the inlet of evaporator 16, as illustrated in FIG. 16.In this embodiment, evaporator 16 comprises first evaporative line 328,evaporator coil 21, and second evaporative line 330. First evaporativeline 328 is positioned between outlet 248 and evaporator coil 21, asillustrated in FIG. 16. Second evaporative line 330 is positionedbetween evaporative coil 21 and temperature sensor 32. Evaporator coil21 is any conventional coil that absorbs heat. Multifunctional valve 225is preferably connected with and adjacent evaporator 16. In onepreferred embodiment, evaporator 16 comprises a portion ofmultifunctional valve 225, such as first inlet 244, outlet 248, andcommon chamber 246, as illustrated in FIG. 16. Preferably, expansionvalve 42 is positioned adjacent evaporator 16. Heat transfer fluid exitsexpansion valve 42 and then directly enters evaporator 16 at inlet 244.As the heat transfer fluid exits expansion valve 42 and entersevaporator 16 at inlet 244, the temperature of the heat transfer fluidis at an evaporative temperature, that is the heat transfer fluid beginsto absorb heat upon passing through expansion valve 42.

Upon passing through inlet 244, common chamber 246, and outlet 248, theheat transfer fluid enters first evaporative line 328. Preferably, firstevaporative line 328 is insulated. Heat transfer fluid then exits firstevaporative line 328 and enters evaporative coil 21. Upon exitingevaporative coil 21, heat transfer fluid enters second evaporative line330. Heat transfer fluid exists in second evaporative line 330 andevaporator 16 at temperature sensor 32.

Preferably, every element within evaporator 16, such as saturated vaporline 28, multifunctional valve 225, and evaporator coil 21, absorbsheat. In one preferred embodiment, as the heat transfer fluid passesthrough expansion valve 42, the heat transfer fluid is at a temperaturewithin 20° F. of the temperature of the heat transfer fluid within theevaporator coil 21. In another preferred embodiment, the temperature ofthe heat transfer fluid in any element within evaporator 16, such assaturated vapor line 28, multifunctional valve 225, and evaporator coil21, is within 20° F. of the temperature of the heat transfer fluid inany other element within evaporator 16. While the above embodiments weredescribed in reference to multifunctional valve 225, any multifunctionalvalve described herein, can be used as well.

In one preferred embodiment, vapor compression system 410 includes acompressor 412, a condenser 414, an evaporator 416, an XDX valve 418,and a metering unit 449, as illustrated in FIG. 20. XDX valve 418 is anydevice known to one of ordinary skill in the art that can be used tometer the flow of heat transfer fluid an that can convert the heattransfer fluid into a saturated vapor upon entering evaporator 16, asdescribed in the above embodiments. Examples of XDX valve 418 aremultifunctional valves 18, 90, 94, 110 and 225, recovery valve 19, anymetering unit coupled to a relatively short liquid line and a relativelylong saturated vapor line sufficient in length and diameter to vaporizea portion of the heat transfer fluid before the heat transfer fluidenters the evaporator, as described herein, and any metering unit inwhich a heat source is applied to the heat transfer fluid in thesaturated vapor line sufficient to vaporize a portion of the heattransfer fluid before the heat transfer fluid enters the evaporator, asdescribed herein. Metering unit 449 can be any device known to one ofordinary skill in the art that can be used to meter the flow of heattransfer fluid, such as a thermostatic expansion valve, a capillarytube, a fast-action capillary tube 500, or a pressure control.

Compressor 412 is coupled to condenser 414 by a discharge line 420. XDXvalve 418 includes first inlet 461, second inlet 462 and outlet 463.Metering unit 449 includes inlet 464 and outlet 465. First inlet 461 ofXDX valve 418 and inlet 464 of metering unit 449 are coupled tocondenser 414 by a bifurcated liquid line 422.

A saturated vapor line 428 couples outlet 463 of XDX valve 418 to inlet455 of evaporator 416, and a suction line 430 couples the outlet ofevaporator 416 to the inlet of compressor 412. A refrigerant line 456couples outlet 465 of metering unit 449 to inlet 455 of evaporator 416.A temperature sensor 432 is mounted to suction line 430 and is operablyconnected to XDX valve 418 and metering unit 449. Temperature sensor 432relays temperature information through a control line 433 to XDX valve418 and through a second control line 434 to metering unit 449.

In accordance with one preferred embodiment, the flow of heat transferfluid from condenser 414 to evaporator 416 can be directed to go througheither XDX valve 418 or metering unit 449. Preferably, the flow of heattransfer fluid from condenser 414 to evaporator 416 can be directed togo through either XDX valve 418 or metering unit 449 based on theconditions of the ambient surroundings 470. Ambient surroundings 470 isthe area or space in which the conditions, such as temperature andhumidity, are controlled or altered by vapor compression system 410. Forexample, if vapor compression system 410 was an air conditioning unit,then ambient surroundings 470 would be defined by the area within abuilding or house being cooled by the air conditioning unit. Moreover,if vapor compression system 410 was a refrigeration unit, for example,then ambient surroundings 470 would be the area within a freezer or arefrigerator being cooled by the refrigeration unit.

In one preferred embodiment, a sensor 460 is located in ambientsurroundings 470 and measures the conditions of ambient surroundings470. Sensor 460 is any metering device known to one of ordinary skill inthe art that can measure the conditions of ambient surroundings 470,such as a pressure sensor, a temperature sensor, or a sensor thatmeasures the density of the fluid. Sensor 460 relays information througha control line 481 to metering unit 449 and through a second controlline 483 to XDX valve 418. In this way, sensor 460 is able to direct theheat transfer fluid to run either through XDX valve 418 or metering unit449 based upon the conditions of ambient surroundings 470.

In one preferred embodiment, sensor 460 is located in ambientsurroundings 470 and measures the humidity of ambient surroundings 470.A desired humidity level is programmed into sensor 460. Upon determiningthe humidity of ambient surroundings 470, sensor 460 then decideswhether to direct the flow of heat transfer fluid to either XDX valve41.8 or metering unit 449 based upon the desired humidity levelprogrammed into sensor 460. If the desired humidity level is less thanthe actual humidity of the ambient surroundings 470, sensor 460 directsthe flow of heat transfer fluid to flow through metering unit 449 byclosing first inlet 461, and by opening inlet 464. By directing the heattransfer fluid to flow through metering unit 449, vapor compressionsystem 410 operates in what will be referred to as a conventionalrefrigeration cycle. When vapor compression system 410 operates in aconventional refrigeration cycle, the amount of humidity in the ambientsurroundings 470 is decreased. If the desired humidity level is greaterthan the actual humidity of the ambient surroundings 470, sensor 460directs the flow of heat transfer fluid to flow through XDX valve 418 byopening first inlet 461, and by closing inlet 464. By directing the heattransfer fluid to flow through XDX valve 418, vapor compression system410 operates in what will be referred to as an XDX cycle. When vaporcompression system 410 operates in an XDX cycle, the amount of humidityin the ambient surroundings 470 increases.

In one preferred embodiment, gating valves 471 and 474 are located atfirst inlet 461 and inlet 464, respectively, as illustrated in FIG. 20.Preferably, gating valves 471 and 474 are solenoid valves capable ofterminating the flow of heat transfer fluid through a passageway, suchas liquid line 422, in response to an electrical signal. However, gatingvalves may be any valve capable of terminating the flow of heat transferfluid through a passageway known to one of ordinary skill, such as avalve that is mechanically activated. Gating valves 471 and 474 can beused to open or close first inlet 461 and inlet 464 at any time eithermechanically or in response to an electrical signal.

In one preferred embodiment, sensor 460 decides whether to direct theflow of heat transfer fluid to either XDX valve 418 or metering unit 449based upon the temperature of the ambient surroundings 470. A desiredtemperature level for the ambient surroundings 470 must first beprogrammed into sensor 460. Sensor 460 directs the flow of heat transferfluid to flow through metering unit 449 by closing first inlet 461 andby opening inlet 464. By directing the heat transfer fluid to flowthrough metering unit 449, vapor compression system 410 operates in whatwill be referred to as a conventional refrigeration cycle. When vaporcompression system 410 operates in a conventional refrigeration cycle,the load capacity of vapor compression system 410 is decreased. If thedesired temperature level cannot be reached after a predetermined timeinterval, then sensor 460 directs the flow of heat transfer fluid toflow through XDX valve 418 by opening first inlet 461 and by closinginlet 464. By directing the heat transfer fluid to flow through XDXvalve 418, vapor compression system 410 operates in what will bereferred to as an XDX cycle. When vapor compression system 410 operatesin an XDX cycle, the load capacity of vapor compression system 410 isincreased.

Varying the load capacity of vapor compression system 410 allows vaporcompression system 410 to be more accurately sized for cooling ambientsurroundings 470. For example, if ambient surroundings 470 needs to becooled in a range which varies from an average amount of ° C. to amaximum amount of ° C., vapor compression system 410 must be sized tocool ambient surroundings 470 by at least the maximum amount of ° C. sothat vapor compression system 410 can achieve the desired temperaturelevel even when the difference between the temperature level of theambient surroundings 470 and the desired temperature level is themaximum amount of ° C. However, this means that vapor compression system410 must be sized larger than required, since more often than not vaporcompression system 410 need only cool ambient surroundings by theaverage amount of ° C. However, by varying the load capacity of vaporcompression system 410, as described above, vapor compression system 410can be sized so that it cools ambient surroundings by the average amountof ° C. when operating vapor compression system 410 in a conventionalrefrigeration cycle, and up to the maximum amount of ° C. when operatingvapor compression system 410 in an XDX cycle.

While the above use of sensor 460 to direct the flow of heat transferfluid to either XDX valve 418 or metering unit 449 has been described asbeing in response to the humidity level or the temperature level of theambient surroundings, sensor 460 may direct the flow of heat transferfluid to either XDX valve 418 or metering unit 449 in response to anyvariable or condition. Moreover, while the above use of vaporcompression system 410 has required a sensor 460 to direct the flow ofheat transfer fluid to either XDX valve 418 or metering unit 449, theflow may be manually directed to either XDX valve 418 or metering unit449, or directed to either XDX valve 418 or metering unit 449 in any oneof a number of ways known to one of ordinary skill in the art, for anyone of a number of reasons.

In one preferred embodiment, discharge line 420 is coupled to bothsecond inlet 462 of XDX valve 418 and condenser 414, to facilitate thedefrosting of evaporator 416. Preferably, discharge line 420 isbifurcated so as to allow discharge line 420 to be simultaneouslycoupled to both second inlet 462 of XDX valve 418 and condenser 414, asillustrated in FIG. 20. Gating valve 472 is located at second inlet 462so as to control the flow of heat transfer fluid from compressor 412 tosecond inlet 462. In order to defrost the coils of evaporator 416,gating valves 472 is opened, and gating valves 471 and 474 are closed toallow heat transfer fluid from compressor 412 to enter evaporator 416and defrost evaporator 416.

In one preferred embodiment, vapor compression system 10 includes aturbulent line 600 before the inlet of evaporator 16, as illustrated inFIG. 22. Turbulent line 600 includes an inlet 634, an outlet 635, and apassageway 630 connecting inlet 634 to outlet 635. Turbulent line 600also includes dimples 605 located on the interior surface 615 ofpassageway 630 of turbulent line 600. Dimples 605 convert the flow ofheat transfer fluid from a laminar flow to a turbulent flow. Byconverting heat transfer fluid to a turbulent flow before heat transferfluid enters evaporator 16, the efficiency of evaporator 16 isincreased. Dimples 605 may either be ridges 610 which project inwardstowards the flow 625 of the heat transfer fluid or bumps 620 whichproject outwards and away from the flow 625 of heat transfer fluid, asillustrated in FIG. 22.

Preferably, turbulent line 600 is position between the metering unit,such as multifunctional valve 18, 90, 94, 110 or 225, recovery valve 19,XDX valve 418, or any conventional metering unit used to meter the flowof heat transfer fluid upon entering evaporator. The placement, size,and spacing of ridges 610 to create a turbulent flow depends on thediameter and length of turbulent line 600 along with the flow rate ofthe heat transfer fluid and the type of heat transfer fluid being used,all which are factors that can be determined by one of ordinary skill inthe art. In one preferred embodiment, the line connecting the meteringunit to the inlet of evaporator 16, referred to herein as either thesaturated vapor line or the refrigerant line, includes turbulent line600. Preferably, a portion of saturated vapor line or refrigerant lineincludes turbulent line 600.

As known by one of ordinary skill in the art, every element of vaporcompression system 10 described above, such as evaporator 16, liquidline 22, and suction line 30, can be scaled and sized to meet a varietyof load requirements. In addition, the refrigerant charge of the heattransfer fluid in vapor compression system 10, may be equal to orgreater than the refrigerant charge of a conventional system.

Another embodiment of the present invention provides a high operatingefficiency vapor compression system including an evaporator having morethan one circuit. When operated according to the method of the presentinvention, such a system dispenses with the need for a distributor topartition the heat transfer fluid to the multiple circuits of theevaporator without the accompanying large loss in evaporator capacitytypically seen when a conventional system is operated without adistributor.

In many applications, it is preferred to distribute heat transfer fluidfrom the expansion device into the circuits of a multi-circuitevaporator coil. In such applications, it is important to distribute theheat transfer fluid equally to each circuit of the evaporator coil. Ifthis is not done, one or more circuits of the evaporator can becomestarved of heat transfer fluid. In such a situation, the evaporatorcapacity is reduced.

In conventional systems having a multi-circuit evaporator, if a simplemanifold divider is used to partition the heat transfer fluid flow intothe multiple evaporator circuits, the circuits of the evaporator coiltend not receive equal amounts of heat transfer fluid. Such a situationis illustrated in FIG. 23. This figure shows three manifoldconfigurations: an up-feed manifold (23(a)), a down-feed manifold(23(b)) and a side-feed manifold (23(c)).

The up-feed manifold receives heat transfer fluid at an input situatedbelow multiple outputs. The down-feed manifold receives heat transferfluid at an input situated above multiple outputs. The side-feedmanifold receives heat transfer fluid at an input situated above some ofthe outputs but below other outputs. In each configuration, heattransfer fluid flows along the path of least resistance from themanifold input to the manifold output. As illustrated in FIG. 23, thoseoutputs closest to the input, or lower than the input, tend to receive agreater portion of the heat transfer fluid than do the other outputs.

Many conventional systems include a “distributor” in an attempt toevenly distribute heat transfer fluid from an expansion device to thecoils of a multi-coil evaporator. Typically, a distributor includes anozzle positioned to focus heat transfer fluid flow evenly into adispersion cone. Output passages are spaced evenly around the cone toreceive the heat transfer fluid.

As illustrated in FIG. 24, expanded heat transfer fluid is deliveredfrom an expansion device (801) to the distributor nozzle (802). Uponpassing though the nozzle, the velocity of the heat transfer fluid isincreased. The heat transfer fluid enters the distributor dispersioncone (803), where it is distributed between multiple distributor outputs(804). The distributor outputs (804) are positioned so that eachdistributor output receives an equal quantity of heat transfer fluid.Each distributor output delivers heat transfer fluid to one circuit ofan evaporator coil (805). Although the inclusion of a distributor tendsto equalize the flow of heat transfer fluid to the coils of amulti-circuit evaporator, and hence maintain the evaporator efficiency,the cost of the distributor invariably increases the cost of the vaporcompression system.

In the method of the invention, the expanded heat transfer fluid isconverted to a high quality liquid vapor mixture before delivery to theevaporator. Example III shows the results of a test performed using sucha method and also using the conventional method of operation, i.e. wherethe expanded heat transfer fluid is not converted to a high qualityliquid vapor mixture before delivery to the evaporator. Despite theabsence of a distributor, conversion of the expanded heat transfer fluidto a high quality liquid vapor mixture before delivery to the evaporatorallowed the evaporator capacity to be maintained. This was the case evenwith a reduction in the heat transfer surface of the evaporator.

In another embodiment of the invention, the increased efficiencyobtained when a vapor compression system is operated according to themethod of the present invention allows for a reduction in the heattransfer fluid load used in the system.

In another embodiment of the invention, the “heat transfer surface” ofthe evaporator coil is smaller than the heat transfer surface of anevaporator coil, manufactured from the same material, required to obtainan equivalent evaporator capacity when a significant amount of theliquid heat transfer fluid is not converted from a liquid form to a highquality liquid vapor mixture. For example, for an evaporator coilmanufactured from a material such as copper, having a given diameter andwall thickness, the length of the evaporator coil may be reduced if thevapor compression system is operated according to the method of thepresent invention. For the purposes of the present invention, the “heattransfer surface” is the area of the evaporator coil in contact with theheat transfer fluid.

Evaporator capacity and mass flow rate are the principal measures ofperformance of refrigerant evaporators. Evaporator capacity is definedas the work done in terms of heat transfer fluid vaporized per hour. TheMass Flow Rate is the mass of heat transfer fluid that moves through theevaporator coil to be vaporized. Evaporator capacity commonly takes intoconsideration the amount of heat transfer fluid flow, the amount of heatremoved, and the heat transfer rate. The expansion device size, theamount of heat transfer fluid in the system and the compressor capacityare each often used to commercially identify the mass flow rate.

Evaporator capacity is viewed as:Q=U*A*(ΔT(log mean)), where

The evaporator capacity, Q, through the heating surface of an-evaporatoris the product of three factors;

A (m²)−the heat transfer surface,

U(Wm⁻²K⁻¹)−the overall heat transfer coefficient, and

ΔT (log mean)−the overall temperature driving force(log mean).

The temperature driving force is a function of the refrigerantproperties, the amount of refrigerant, and the amount of heat absorbed.The Overall Heat Transfer Coefficient is a function of the design of theevaporator. Factors affecting the Overall Heat Transfer Coefficient (U)include:

-   -   the frost or condensing coefficient on the outside of the        evaporator coil (ho),    -   the thermal resistance of the evaporator coil (R),    -   the liquid film heat transfer coefficient on the inside of the        evaporator coil (hi),    -   the thermal resistance of oil deposits on the inside of the        evaporator coil,    -   the thermal resistance of dirt on the outside of the evaporator        coil, and    -   miscellaneous other factors, such as the amount of moisture in        the air.

Without further elaboration it is believed that one skilled in the artcan, using the preceding description, utilize the invention to itsfullest extent. The following examples are merely illustrative of theinvention and are not meant to limit the scope in any way whatsoever.

EXAMPLE I

A 5-ft (1.52 m) Tyler Chest Freezer was equipped with a multifunctionalvalve in a refrigeration circuit, and a standard expansion valve wasplumbed into a bypass line so that the refrigeration circuit could beoperated as a conventional vapor compression system and as an XDXrefrigeration system arranged in accordance with the invention. Therefrigeration circuit described above was equipped with a saturatedvapor line having an outside tube diameter of about 0.375 inches (0.953cm) and an effective tube length of about 10 ft (3.048 m). Therefrigeration circuit was powered by a Copeland hermetic compressorhaving a capacity of about ⅓ ton (338 kg) of refrigeration. A sensingbulb was attached to the suction line about 18 inches from thecompressor. The circuit was charged with about 28 oz. (792 g) of R-12refrigerant available from The DuPont Company. The refrigeration circuitwas also equipped with a bypass line extending from the compressordischarge line to the saturated vapor line for forward-flow defrosting(See FIG. 1). All refrigerated ambient air temperature measurements weremade using a “CPS Date Logger” by CPS temperature sensor located in thecenter of the refrigeration case, about 4 inches (10 cm) above thefloor.

XDX System—Medium Temperature Operation

The nominal operating temperature of the evaporator was 20° F. (−6.7°C.) and the nominal operating temperature of the condenser was 120° F.(48.9° C.). The evaporator handled a cooling load of about 3000 Btu/hr(21 g cal/s). The multifunctional valve metered refrigerant into thesaturated vapor line at a temperature of about 20° F. (−6.7° C.). Thesensing bulb was set to maintain about 25° F. (13.9° C.) superheating ofthe vapor flowing in the suction line. The compressor dischargedpressurized refrigerant into the discharge line at a condensingtemperature of about 120° F. (48.9° C.), and a pressure of about 172lbs/in² (118,560 N/m²).

XDX System—Low Temperature Operation

The nominal operating temperature of the evaporator was −5° F. (−20.5°C.) and the nominal operating temperature of the condenser was 115° F.(46.1° C.). The evaporator handled a cooling load of about 3000 Btu/hr(21 g cal/s). The multifunctional valve metered about 2975 ft/min (907km/min) of refrigerant into the saturated vapor line at a temperature ofabout −5° F. (−20.5° C.). The sensing bulb was set to maintain about 20°F. (11.1° C.) superheating of the vapor flowing in the suction line. Thecompressor discharged about 2299 ft/min (701 m/min) of pressurizedrefrigerant into the discharge line at a condensing temperature of about115° F. (46.1° C.), and a pressure of about 161 lbs/in² (110,977 N/m²).The XDX system was operated substantially the same in low temperatureoperation as in medium temperature operation with the exception that thefans in the Tyler Chest Freezer were delayed for 4 minutes followingdefrost to remove heat from the evaporator coil and to allow waterdrainage from the coil.

The XDX refrigeration system was operated for a period of about 24 hoursat medium temperature operation and about 18 hours at low temperatureoperation. The temperature of the ambient air within the Tyler ChestFreezer was measured about every minute during the 23 hour testingperiod. The air temperature was measured continuously during the testingperiod, while the vapor compression system was operated in bothrefrigeration mode and in defrost mode. During defrost cycles, therefrigeration circuit was operated in defrost mode until the sensingbulb temperature reached about 50° F. (10° C.). The temperaturemeasurement statistics appear in Table I below.

Conventional System—Medium Temperature Operation With Electric Defrost

The Tyler Chest Freezer described above was equipped with a bypass lineextending between the compressor discharge line and the suction line fordefrosting. The bypass line was equipped with a solenoid valve to gatethe flow of high temperature refrigerant in the line. An electric heatelement was energized instead of the solenoid during this test. Astandard expansion valve was installed immediately adjacent to theevaporator inlet and the temperature sensing bulb was attached to thesuction line immediately adjacent to the evaporator outlet. The sensingbulb was set to maintain about 6° F. (3.33° C.) superheating of thevapor flowing in the suction line. Prior to operation, the vaporcompression system was charged with about 48 oz. (1.36 kg) of R-12refrigerant.

The conventional vapor compression system was operated for a period ofabout 24 hours at medium temperature operation. The temperature of theambient air within the Tyler Chest Freezer was measured about everyminute during the 24 hour testing period. The air temperature wasmeasured continuously during the testing period, while the vaporcompression system was operated in both refrigeration mode and inreverse-flow defrost mode. During defrost cycles, the refrigerationcircuit was operated in defrost mode until the sensing bulb temperaturereached about 50° F. (10°C.). The temperature measurement statisticsappear in Table I below.

Conventional System—Medium Temperature Operation With Air Defrost

The Tyler Chest Freezer described above was equipped with a receiver toprovide proper liquid supply to the expansion valve and a liquid linedryer was installed to allow for additional refrigerant reserve. Theexpansion valve and the sensing bulb were positioned at the samelocations as in the reverse-flow defrost system described above. Thesensing bulb was set to maintain about 8° F. (4.4° C.) superheating ofthe vapor flowing in the suction line. Prior to operation, the vaporcompression system was charged with about 34 oz. (0.966 kg) of R-12refrigerant.

The conventional vapor compression system was operated for a period ofabout 24½ hours at medium temperature operation. The temperature of theambient air within the Tyler Chest Freezer was measured about everyminute during the 24½ hour testing period. The air temperature wasmeasured continuously during the testing period, while the vaporcompression system was operated in both refrigeration mode and in airdefrost mode. In accordance with conventional practice, four defrostcycles were programmed with each lasting for about 36 to 40 minutes. Thetemperature measurement statistics appear in Table I below. TABLE IREFRIGERATION TEMPERATURES (° F./° C.) XDX¹⁾ XDX¹⁾ Conventional²⁾Conventional²⁾ Medium Low Electric Air Temperature Temperature DefrostDefrost Average 38.7/3.7 4.7/−15.2 39.7/4.3 39.6/4.2 Standard 0.8 0.84.1 4.5 Deviation Variance 0.7 0.6 16.9 20.4 Range 7.1 7.1 22.9 26.0¹⁾one defrost cycle during 23 hour test period²⁾three defrost cycles during 24 hour test period

As illustrated above, the XDX refrigeration system arranged inaccordance with the invention maintains a desired the temperature withinthe chest freezer with less temperature variation than the conventionalsystems. The standard deviation, the variance, and the range of thetemperature measurements taken during the testing period aresubstantially less than the conventional systems. This result holds foroperation of the XDX system at both medium and low temperatures.

During defrost cycles, the temperature rise in the chest freezer wasmonitored to determine the maximum temperature within the freezer. Thistemperature should be as close to the operating refrigerationtemperature as possible to avoid spoilage of food products stored in thefreezer. The maximum defrost temperature for the XDX system and for theconventional systems is shown in Table II below. TABLE II MAXIMUMDEFROST TEMPERATURE (° F./° C.) XDX Conventional Conventional MediumTemperature Electric Defrost Air Defrost 44.4/6.9 55.0/12.8 58.4/14.7

EXAMPLE II

The Tyler Chest Freezer was configured as described above and furtherequipped with electric defrosting circuits. The low temperatureoperating test was carried out as described above and the time neededfor the refrigeration unit to return to refrigeration operatingtemperature was measured. A separate test was then carried out using theelectric defrosting circuit to defrost the evaporator. The time neededfor the XDX system and an electric defrost system to complete defrostand to return to the 5° F. (−15° C.) operating set point appears inTable III below. TABLE III TIME NEEDED TO RETURN TO REFRIGERATIONTEMPERATURE OF 5° F. (−15° C.) FOLLOWING Conventional System XDX withElectric Defrost Defrost Duration (min) 10 36 Recovery Time (min) 24 144

As shown above, the XDX system using forward-flow defrost through themultifunctional valve needs less time to completely defrost theevaporator, and substantially less time to return to refrigerationtemperature.

EXAMPLE III

A three door reach in freezer was set up in two configurations andtested to determine the ability of the freezer to meet definedacceptance criteria under each configuration. The tests were conductedusing a Three-door Reach-In freezer powered by a Copeland compressor(part number KAKD-011E-CAV) and loaded with 24 ozs of R-404Arefrigerant. The compression circuit used a FSE-1/2-ZP35 expansionvalve. In the unmodified configuration, the system capacity was rated bythe manufacturer at 4,280 BTU/hr and the evaporator capacity at 3,500BTU/hr.

In the first (unmodified) configuration, the freezer was operated as aconventional vapor compression system, i.e. without the conversion ofthe heat transfer fluid to a high quality liquid vapor mixture beforedelivery to the evaporator. In this configuration, the evaporator coilconsisted of a total of forty-two (42) passes of ⅜″ copper tubing. Theevaporator coil was fed by a double feed through a distributor.

In the second (modified) configuration, the freezer was operatedaccording to the method of the present invention, i.e. portions of theheat transfer fluid were converted to a high quality liquid vapormixture before delivery to the evaporator. In this configuration, theevaporator coil consisted of a total of twenty-eight passes of ⅜″ coppertubing. The evaporator coil was fed directly by a double feed without adistributor.

The test conditions were those set by Underwriters Laboratories as perNSF-7, 6.2. The test requires that a freezer shall be capable ofmaintaining an air temperature of 0° F. (−18° C.) or less in all freezercompartment interiors under defined environmental conditions.

The testing criteria require that, prior to the start of the test, thefreezer is allowed to establish thermal equilibrium according to themanufacturer's instructions or cycle on and off at least two full cyclesat an ambient temperature of 73±3° F. (22±2° C.). The test must beconducted within a test chamber maintained under the followingconditions for the duration of the test:

ambient temperature of 100±3° F.° (38±2° C.); and

no vertical temperature gradient exceeding 1.5° F./ft (2.5° C./m).

Air temperatures within the empty freezer compartment must be monitoredusing remote sensing devices (thermocouples) accurate to a ±1° F. (0.5°C.). The thermocouples must be positioned as close as possible to thefollowing locations: Thermocouple #1: (when facing the front of theunit) 5±0.25 in (127±6 mm) from the left interior wall, 2+0.25 in (51+6mm) above the bottom horizontal plane of the cooling unit, (for units inwhich the evaporator is not suspended from the ceiling, the thermocoupleshall be placed 5+0.25 in [127±6 mm] down from the ceiling) and centeredfront-to-back;

Thermocouple #2: centered front-to-back, centered top-to-bottom,centered left-to-right; and

Thermocouple #3: (when facing the unit) 5±0.25 in (127±6 mm) from theright interior wall, 5±0.25 (127±6 mm) above the internal floor of theunit, and centered front-to-back.

Prior to recording the air temperatures, the unit must be operated fortwo complete refrigeration cycles at the test chamber ambientconditions. The temperature at each thermocouple location must then berecorded at 5-minute intervals over a period of 4 hours.

The time during which the freezer's compressor(s) is operating must bemonitored over the complete test duration, and the compressor percentagerun time must be calculated for each compressor using the formula:Compressor percentage run time, R=d/D×100, where: “d” is the elapsedtime that the compressor is operating during a whole number of cycles;and “D” is the total elapsed time during a whole number of cycles.

In order to meet the acceptance criteria, the temperature at eachthermocouple location within each freezer compartment must not exceed 0°F. (−18° C.) during the 4-hour test period, and the compressorpercentage run time must not exceed 80%.

As shown in Table IV, the conventional system achieved the acceptancecriteria, having a compressor run time percentage of 75%. Table V showsthat the XDX (modified) system, i.e. the system operated so that theheat transfer fluid was converted to a high quality liquid vapor mixturebefore delivery to the evaporator, also achieved the acceptancecriteria, even though no distributor was included to equalize thedelivery of heat transfer fluid to the evaporator and the heat transfersurface is smaller that in the freezer operated by the conventional(unmodified) method. In addition, the compressor percentage runtime forthe XDX (modified) system was less than that of the conventional system.TABLE IV Conventional (unmodified) System - 42-pass Evaporator Thermo-Thermo- Thermo- couple 1 couple 2 couple 3 % Runtime Max. Temp. (° F.)−0.56 −1.12 0.27 Average Temp. −5.32 −5.77 −6.82 (° F.) Min. temp. (°F.) −9.12 −9.68 −11.34 Compressor 75 Runtime

TABLE 5 XDX (modified) System - 28-pass Evaporator Thermo- Thermo-Thermo- couple 1 couple 2 couple 3 % Runtime Max. Temp. (° F.) −0.52−0.97 0.07 Average Temp. −4.52 −5.07 −5.36 (° F.) Min. temp. (° F.)−8.27 −8.94 −9.78 Compressor 64 Runtime

Thus, it is apparent that there has been provided, in accordance withthe invention, a vapor compression system that fully provides theadvantages set forth above. Although the invention has been describedand illustrated with reference to specific illustrative embodimentsthereof, it is not intended that the invention be limited to thoseillustrative embodiments. Those skilled in the art will recognize thatvariations and modifications can be made without departing from thespirit of the invention. For example, non-halogenated refrigerants canbe used, such as ammonia, and the like can also be used. It is thereforeintended to include within the invention all such variations andmodifications that fall within the scope of the appended claims andequivalents thereof.

1. A method of operating a vapor compression system, comprising:compressing a heat transfer fluid in a compressor; condensing the heattransfer fluid in a condenser; expanding the heat transfer fluid in anexpansion device to form an expanded heat transfer fluid; supplying theexpanded heat transfer fluid to a first evaporative line of anevaporator, wherein the evaporator comprises the first evaporative lineand an evaporator coil and wherein the expansion device is in fluidcommunication with the evaporator coil via the first evaporative line;converting a portion of a liquid form of the expanded liquid heattransfer fluid to a high quality liquid vapor mixture within the firstevaporative line; supplying the high quality liquid vapor mixture to theevaporator coil, converting a portion of a liquid form of the highquality liquid vapor mixture to a vapor form within the evaporator coil;and returning the heat transfer fluid to the compressor by a suctionline.
 2. The method of claim 1, wherein the heat transfer fluid isreceived by the evaporator coil as a saturated vapor.
 3. The method ofclaim 1, wherein the heat transfer fluid is received by the evaporatorcoil in a turbulent state.
 4. The method of claim 1, wherein theexpansion device forms part of a multifunctional valve.
 5. The method ofclaim 4, wherein the multifunctional valve is adjacent to theevaporator.
 6. The method of claim 4, wherein the evaporator furthercomprises a portion of the multifunctional valve.
 7. The method of claim1, wherein the expansion device forms part of a recovery valve.
 8. Themethod of claim 1, wherein a temperature sensor is mounted to thesuction line and is operatively connected to the expansion device. 9.The method of claim 8, wherein the heat transfer fluid undergoesexpansion at the expansion device at a rate determined by a temperatureof the suction line at the temperature sensor.
 10. The method of claim1, wherein the heat transfer fluid expanded within the expansion deviceis not passed through a distributor before delivery to the evaporatorcoil.
 11. The method of claim 1, wherein, at a fixed cooling load, theheat transfer fluid within the expansion device and the heat transferfluid within the evaporator are at a temperature within 20 deg F. 12.The method of claim 6, wherein, at a fixed cooling load, the heattransfer fluid within the multifunctional valve and the heat transferfluid within the evaporator are at a temperature within 20 deg F.
 13. Amethod of operating a vapor compression system, comprising: compressinga heat transfer fluid in a compressor; condensing the heat transferfluid in a condenser; expanding the heat transfer fluid in an expansiondevice to form an expanded heat transfer fluid; supplying the expandedheat transfer fluid to an evaporator comprising an evaporator coilhaving a heat transfer surface; converting a portion of a liquid form ofthe expanded heat transfer fluid to a high quality liquid vapor mixtureprior to delivery to the evaporator coil; converting a portion of aliquid form of the high quality liquid vapor mixture to a vapor formwithin the evaporator coil; and returning the heat transfer fluid to thecompressor by a suction line.
 14. The method of claim 13 wherein, at afixed cooling load, the heat transfer surface of the evaporator coil issmaller than that required to obtain an equivalent evaporator capacitywhen the portion of the liquid form of the expanded heat transfer fluidis not converted from the liquid form to the high quality liquid vapormixture prior to delivery to the evaporator coil.
 15. The method ofclaim 13 wherein, at a fixed cooling load, the conversion of the portionof the liquid heat transfer fluid from a liquid form to a high qualityliquid vapor mixture prior to delivery to the evaporator coil results ina decreased variation in refrigerated air temperature when compared to amethod in which the portion of the liquid form of the expanded heattransfer fluid is not converted from the liquid form to the high qualityliquid vapor mixture prior to delivery to the evaporator coil.
 16. Themethod of claim 13 wherein, at a fixed cooling load, less power isrequired to power the compressor than is required when the portion ofthe liquid form of the expanded heat transfer fluid is not convertedfrom the liquid form to the high quality liquid vapor mixture prior todelivery to the evaporator coil.
 17. The method of claim 13, wherein, ata fixed cooling load, the heat transfer fluid within the expansiondevice and the heat transfer fluid within the evaporator are at atemperature within 20 deg F.
 18. The method of claim 13, wherein theexpansion device forms part of a multifunctional valve.
 19. The methodof claim 18, wherein the multifunctional valve is adjacent to theevaporator.
 20. The method of claim 18, wherein the evaporator furthercomprises a portion of the multifunctional valve.